Chance of devastating tsunami small in Florida

March 11, 2011|By Kevin Spear, Orlando Sentinel

The odds are low that Florida would get hit by a tsunami like the one on Friday that devastated Japan, killing hundreds of people.

"It's not zero," said Bart Hagemeyer, longtime meteorologist-in-charge at the National Weather Service office in Melbourne. "But the possibility of a tsunami hitting Florida's East Coast is very small."

Most tsunamis, also called seismic sea waves, occur in the Pacific and Indian oceans. In those regions, various plates of the Earth's crust grind and joust against each other as one slides over another, breeding earthquakes.

The resulting shock of a temblor can propel a wave that will cross an entire ocean, at jet speeds and often imperceptible to ships, before it slows to a relative crawl and rises in a towering wall of water.

The history of big waves hitting Florida is short.

A powerful earthquake in Portugal in 1755 killed thousands there and launched a tsunami that hit much of the U.S. coast. Scientists don't know if that caused many deaths in Florida, which was sparsely populated at the time.

An earthquake in Charleston, S.C., in 1886 triggered a wave that surged up the St. Johns River to Jacksonville, causing few if any deaths.

And there was strange incident of a rogue, 18-foot wave that flooded the parked cars of sunbathers on Daytona Beach without warning in 1992. Scientists blamed that on an undersea avalanche, not an earthquake, but it drew much attention.

Florida does have a natural defense against a tsunami. The state's shallow, coastal waters will act as a breakwater, dissipating some of the powerful wave's energy.

Even though the risk is low, Hagemeyer, other experts and some communities don't ignore the danger. Indian Harbour Beach qualified in 2005 as the U.S. East Coast's first city prepared for a tsunami. The Naval Station Mayport near Jacksonville also holds the designation, and Brevard and Volusia counties include tsunami preparedness in their emergency-management plans.

"We've had some people criticize us and say 'You guys are crazy – why do you bother? You're just scaring people,'" said Jackie Burns, city manager at Indian Harbour Beach, a Brevard County community of about 2 square miles and 8,800 residents.

To qualify for a National Weather Service TsunamiReady designation, the city installed warning lights along the beach, hooked up a siren and drew up evacuation plans to be carried out by police and firefighters with bullhorns and loudspeakers.

They drill regularly on what to do when alerted to a tsunami watch or warning – which hasn't happened yet.

Florida also has a short list of what to worry about in the way of tsunami threats.

Geologists are keeping an eye on the Puerto Rico trench in the Caribbean for the possibility of a tectonic plate shift – earthquake – that triggers a tsunami. A deadly tsunami, like the one triggered early last year by a major earthquake in Haiti, is more likely to occur in that region than along the U.S. East Coast.

An eruption of the active Cumbre Vieja volcano in the Canary Islands off Africa is thought to be capable of producing a mega-tsunami that could hit Florida.

And another major earthquake in Portugal continues to be a worry. A tsunami triggered there would take about eight hours to hit Florida, traveling at 475 mph across open ocean.

Since the Indian Ocean earthquake and tsunami in 2004 that killed nearly a quarter-million people, the National Oceanic and Atmospheric Administration has installed dozens of ocean-monitoring buoys, including seven in the Atlantic, Caribbean and Gulf of Mexico.

Those buoys are watching out for Florida around the clock for what may never endanger anybody alive today.

George Maul, director of the Department of Marine Environmental Systems at the Florida Institute of Technology in Melbourne, said that looking only at the probability of a tsunami strike on Florida is misleading.

A better approach, he said, would be to consider the total risk, which includes the potential frequency of tsunami strikes, the vulnerability of damage to buildings and homes, and the preparedness of communities.

Because Florida is poorly prepared, the state's total risk compares to California's, where a strike is more likely but buildings are better designed to withstand one of the waves and residents are better prepared to respond, he said.

That's true except for in Indian Harbour Beach, Maul said.

"They go through regular drills," Maul said. "They know if a tsunami is coming, they know how much time they have to react, they know what to do in order to get people off the beach."